From 76789e6db8533da2ba9fd20cf66573d90ce22b4a Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Mon, 8 Jul 2024 00:07:28 -0700
Subject: partition, split, split*: infinite looping regression.

This is a bug introduced in 9cfa3435 on 2024-02-24.
The underlying cause is lack of test coverage for
these functions.

* lib.c (partition_func, split_func, split_star_func): The
original code iterated through the indies using the pop macro,
thus extracting the next index and stepping in one step.
The iter_begin rewrite wrongly moved the iter_step into one
of the cases. The index iteration must be stepped in the case
where the loop is continued vi continue, otherwise an infinite
loop results.
---
 lib.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib.c b/lib.c
index 52f984e3..c0a4d850 100644
--- a/lib.c
+++ b/lib.c
@@ -4209,6 +4209,8 @@ static val partition_func(val base, val lcons)
                       raw_index);
       val index_rebased = minus(index, base);
 
+      indices = iter_step(indices);
+
       if (le(index_rebased, zero)) {
         continue;
       } else {
@@ -4218,8 +4220,7 @@ static val partition_func(val base, val lcons)
         if (rest) {
           val fun = us_lcons_fun(lcons);
           us_func_set_env(fun, index);
-          us_rplacd(lcons, make_lazy_cons_car_cdr(fun, rest,
-                                                  iter_step(indices)));
+          us_rplacd(lcons, make_lazy_cons_car_cdr(fun, rest, indices));
         } else {
           us_rplacd(lcons, nil);
         }
@@ -4249,6 +4250,8 @@ static val split_func(val base, val lcons)
                       raw_index);
       val index_rebased = minus(index, base);
 
+      indices = iter_step(indices);
+
       if (minusp(index_rebased)) {
         continue;
       } else {
@@ -4259,8 +4262,7 @@ static val split_func(val base, val lcons)
         if (rest) {
           val fun = us_lcons_fun(lcons);
           us_func_set_env(fun, index);
-          us_rplacd(lcons, make_lazy_cons_car_cdr(fun, rest,
-                                                  iter_step(indices)));
+          us_rplacd(lcons, make_lazy_cons_car_cdr(fun, rest, indices));
         } else {
           us_rplacd(lcons, cons(rsub, nil));
         }
@@ -4290,6 +4292,8 @@ static val split_star_func(val base, val lcons)
                       raw_index);
       val index_rebased = minus(index, base);
 
+      indices = iter_step(indices);
+
       if (minusp(index_rebased)) {
         continue;
       } else {
@@ -4300,8 +4304,7 @@ static val split_star_func(val base, val lcons)
         if (rest) {
           val fun = us_lcons_fun(lcons);
           us_func_set_env(fun, succ(index));
-          us_rplacd(lcons, make_lazy_cons_car_cdr(fun, rest,
-                                                  iter_step(indices)));
+          us_rplacd(lcons, make_lazy_cons_car_cdr(fun, rest, indices));
         } else {
           us_rplacd(lcons, cons(rsub, nil));
         }
-- 
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